Application of stereolithographic custom models for studying the impact of biofilms and mineral precipitation on fluid flow.

Here we introduce the use of transparent experimental models fabricated by stereolithography for studying the impacts of biomass accumulation, minerals precipitation, and physical configuration of flow paths on liquid flow in fracture apertures. The internal configuration of the models ranged in complexity from simple geometric shapes to those that incorporate replicated surfaces of natural fractures and computationally derived fracture surfaces. High-resolution digital time-lapse imaging was employed to qualitatively observe the migration of colloidal and soluble dyes through the flow models. In this study, a Sphingomonas sp. and Sporosarcina (Bacillus) pasteurii influenced the fluid dynamics by physically altering flow paths. Microbial colonization and calcite deposition enhanced the stagnant regions adjacent to solid boundaries. Microbial growth and calcite precipitation occurred to a greater extent in areas behind the fabricated obstacles and less in high-velocity orifices.

Defective B cell clonal regulation and autoantibody production in New Zealand black mice.

By using the splenic fragment assay in a KLH-primed host, we have evaluated the clonal anergy model of tolerance in DBA/2 and spontaneously autoimmune NZB mice. Unlike immature B cells from DBA/2 mice (which are tolerized by encounter with TNP-OVA), SIg- B cells from NZB mice respond to TNP-KLH with equal precursor frequency in TNP-OVA-tolerized or control fragments. In additional experiments, SIg- bone marrow or mature spleen cells of DBA/2 or NZB origin were adoptively transferred into irradiated (DBA/2 X NZB) F1 X xid hosts, and host-derived splenic fragments were stimulated in vitro with LPS and growth factors. These experiments revealed a substantial anti-ssDNA precursor frequency in NZB marrow and spleen (2.5 and 5.1, respectively, per 10(7) transferred cells). In DBA/2 SIg- marrow cells, there was an anti-ssDNA precursor frequency of 1.3 to 3.5/10(7) transferred cells; however, anti-ssDNA-producing clones were reduced in fragments derived from recipients of DBA/2 as compared with NZB spleen cells (0.2 to 1.9/10(7) transferred cells). By using a replica plate technique, we evaluated fragments from recipients of DBA/2 SIg- marrow cells or mature spleen cells for anti-TNP reactivity. In fragments derived from recipients of DBA/2 SIg- marrow cells, 92% of anti-TNP-producing fragments also bound ssDNA. In fragments derived from recipients of DBA/2 spleen cells, only 43% of anti-TNP-producing fragments also bound ssDNA. Our findings document that NZB marrow-derived immature B cells abnormally resist tolerance induction, and that clonal anergy/selection operates in directing the B cell repertoire away from autoantibody formation.

Circulatory responses of perinatal goats to prostaglandin precursors.

The effects of precursors in the prostaglandin synthetic pathway as well as those of analogs of cyclic endoperoxide intermediates upon the pulmonary and systemic circulations of fetal and newborn goats were examined. Exogenous arachidonic acid increased pulmonary vascular resistance and decreased systemic arterial pressure of fetuses and newborns. The effects of dihomo-gamma-linolenic acid on the circulation are qualitatively similar, but quantitatively less, than those of arachidonic acid. The cyclic endoperoxide analogs were strong pressors in both pulmonary and systemic circulations. The responses to the fatty acid precursors, which are totally blocked by indomethacin and meclofenamate, appear to indicate that they give rise to more than one vasoactive product. Furthermore, exogenous arachidonic acid produces effects which appear to be different from those produced by endogenous pulmonary arachidonic acid.

Effect of indomethacin on pulmonary vascular response to ventilation of fetal goats.

The effect of indomethacin treatment of the pulmonary vasodilation caused by ventilation of the fetal lung with air was evaluated in anesthetized, exteriorized, fetal goats by means of an open-chest, pump-perfused lung preparation. The decrease in pulmonary vascular resistance that occurs when the fetal lung is ventilated with air consists of two components: 1) a rapid decrease in pulmonary vascular resistance during the first 30 s of ventilation; 2) a slower decline, which continues through the first 10-20 min or more of ventilation. Indomethacin has no effect on the first component. The second component is absent following indomethacin pretreatment. The effect of indomethacin treatment is more pronounced in immature fetuses (less than 90% gestation) than in mature fetuses. Prostaglandin synthase activity appears to be important in the pulmonary vasodilation caused by ventilation of the fetal lungs with air.

Effects of indomethacin on cardiovascular hemodynamics of goats in hemorrhagic shock.

We examined effects of indomethacin, meclofenamate, and prostaglandin E1 on systemic arterial pressure, heart rate, cardiac output, and systemic vascular resistance of anesthetized juvenile goats in severe hemorrhagic shock. Hemorrhagic shock was characterized by low systemic arterial pressure, decreased vascular resistance, and reduction in cardiac output. In acute experiments, indomethacin (3.4 mg/kg) attenuated the systemic hypotension of hemorrhagic shock. The increase in systemic arterial pressure following treatment with indomethacin was the result of increased systemic vascular resistance. Systemic arterial pressure, heart rate, and cardiac output fell during intravenous prostaglandin E1 infusions (3 micrograms/kg/min for 5 min) in both controls and goats in shock. The effects of prostaglandin E1 were more pronounced and prolonged in goats that had undergone the hemorrhagic-shock-producing procedure followed by indomethacin than in control animals treated with indomethacin but not hemorrhaged. Not only was meclofenamate less effective than indomethacin in increasing the systemic arterial pressures of goats in this type of hemorrhagic shock, but also it attenuated the pressor effects of indomethacin. Substances synthesized via prostaglandin fatty acid cyclo-oxygenase may be involved in the systemic hypotension that is characteristic of hemorrhagic shock.

Prostaglandins and regulation of the pulmonary circulation in the perinatal period.

Effects of indomethacin on pulmonary vasodilation caused by ventilation of the fetal lungs with air were evaluated in anesthetized, exteriorized fetal goats by means of an open-chest pump perfused lung preparation. When fetal lungs are ventilated with air, pulmonary vascular resistance decreases in two steps: 1) a rapid decrease in pulmonary vascular resistance during the first 30 seconds of ventilation, and 2) a slower decline which continues through the first 10-20 minutes of more of ventilation. Indomethacin has minimal effect upon the first component. The second component is absent following treatment with indomethacin. Effects observed with indomethacin were more pronounced in immature fetuses (less than 90% gestation), than in mature fetuses. Prostaglandin synthetase activity appears to have a role in the pulmonary vasodilation resulting from ventilation of the fetal lungs with air.

Electrolyte and acid-base status of aqueous humor in perinatal and adult goats.

These experiments were undertaken to determine electrolyte concentration and acid-base status of aqueous humor and arterial plasma H2O in perinatal and adult goats. The distribution of potassium, sodium, chloride, magnesium, and calcium between aqueous humor and plasma H2O in fetal, neonatal, and adult goats changed independently with age and could not be explained by passive Gibbs-Donnan equilibria. Anterior chamber aqueous humor has a reduced pH, PO2, HCO3-, and an elevated PCO2 compared to arterial blood in the neonate and adult.